Foldable beds, and particularly those folding beds which are stored within other furniture items, are an attractive option for consumers with restricted living space. Typically a foldable bed will fold upon itself either one or two times for easy storage, then will unfold into a bed for sleeping. The bed will generally include a mattress that is sufficiently flexible to fold upon itself and a frame which serves as both the supporting bed frame and as a restraining unit for the mattress in its folded position. The frame will include a body section pivotally attached at its ends to the ends of an intermediate cavity section, the opposite ends of which are attached to a seat section; these sections are serially aligned horizontally in the unfolded position, and are folded back upon one another such that the body section and seat section are substantially parallel to one another and are perpendicular to the cavity section. The frame is often mounted in an upholstered sofa or chair frame into which the bed frame and mattress are folded and stored when not in use; cushions are then placed upon the folded mattress for use of the unit as a sofa or chair.
To date, foldable beds have exhibited a number of shortcomings. One general area of dissatisfaction is the sleeping comfort of the bed. For storage purposes, it is desirable that the mattress fold into the thinnest package possible for storage. The need for a compactly folded mattress is most apparent if the mattress and frame are attached to a sofa or chair, since the mattress and frame must fit within the walls of the sofa or chair, which well may have style or ergonomic restrictions. Thick, firm mattresses that would provide suitable sleeping comfort are too bulky to be folded into the compact size required by many sofa or chair styles; in particular, transitional and contemporary styles often require either a low seat height or an "off-the-floor" front profile. Present sofas have addressed the size constraint by using a mattress that is either thin and easily folded into a thin unit, soft and easily crushed into a thin unit, or a combination of each. The result of such compromises is generally an unsatisfactory sleeping surface.
Another problem is the seating comfort of the chair or sofa, which depends not only on the firmness of the seat cushions and the mattress, but also on the folded configuration of the bed frame within the storage chamber of the sofa. The frame supports the lower surface of the mattress from below in the unfolded position; as the bed is folded into the folded position, the portion of the frame that supported the seat section of the bed in the unfolded position inverts to rest on the top edge of the mattress in the folded position. Cushions for a chair or sofa then lie upon the mattress and on the side rail of the seat section of the bed frame. The presence of this side rail beneath the cushion adversely affects the seating comfort of the cushion. As an occupant sits on the cushion, the cushion edge directly over the side rail tends to "ride" the side rail, and as a result the cushion supports the occupant unevenly. Attempts to address this deficiency have included the incorporation of a curved portion in the seat section side rail which bends out of the plane of the upper surface of the mattress, but this has not been entirely successful at providing a uniform, comfortable feel within the seat.
There has also been some dissatisfaction with the operation of the folding mechanism in moving from the folded position to the unfolded position and back. In particular, the smoothness with which the mechanism folds has been criticized, as has the ease of locking the mechanism into and unlocking it from the folded position after the folded bed has been removed from its storage chamber within a sofa. The folding of the bed is affected by the sequence in which the mechanism folds from the unfolded position. Ideally, during folding from the unfolded position to the folded position the seat section begins to pivot about the cavity section essentially simultaneously with any pivoting of the cavity section about the body section. However, linkages that control the folding of the frame do not time the folding of the frame to achieve this folding sequence. Instead, often the cavity section will begin to fold first; consequently, the seat section pivots slightly about the cavity section away from the folded position (i.e., to a position slightly beyond horizontal) before it rotates back toward the folded position. This reverse motion causes a undesirable "catching" jolt that is transmitted to the operator during opening, and, more importantly, can cause the unfolded sofa to fold prematurely into the sofa storage chamber.
The unlocking of the bed from the folded position in many current models is also operationally unsatisfactory. The bed must be locked into the folded position so that it does not unfold while stored within a sofa or closet. Most commonly used is a two-unit "squeeze" locking configuration of linkages which employs a supporting leg as a lever to create within the folding mechanism two substantially "on-center" alignments of three interconnected pivots as the leg folds completely into the folded position. One of the sets of pivots locks the seat section in its folded position relative to the cavity section; the other locks the cavity section into its folded position relative to the body section. See, e.g., U.S. Pat. No. 4,905,328 to Pokorny. Locking mechanisms of this type compress the mattress into the folded position; accordingly, they must be able to withstand the relatively high forces exerted by the compressed mattress to avoid opening prematurely. Consequently, these linkages are generally difficult to unlock, often requiring the operator to jerk vigorously on the leg mechanism to unlock the bed.
Many foldable beds have a head section pivotally connected to the body section at the end thereof opposite the cavity section which folds into a generally vertical position in the folded position. In the unfolded position, the head section is generally movable between a stationary horizontal position aligned with the other frame sections and a releasably locked inclined position which permits the user to read or watch television comfortably while lying on the bed. There are a number of mechanisms in current use which control the inclining and reclining of the head section in the unfolded position, virtually all of which use a mechanism which includes a slotted member along which a "bow-tie" shaped locking member slides and pivots to lock and unlock the headrest into and from the inclined position. This sliding mechanism is somewhat difficult to manufacture consistently and will at times malfunction after repeated use; thus its replacement with a mechanism which operates comparably is desirable.
Accordingly, what is needed is a foldable bed which is comfortable for sleeping and sitting, easily and smoothly operated from the folded and unfolded position, and easily manufactured.